Mycotoxins are toxins produced by funghi that are known to affect adversely the nutrition and health of humans and animals. The production of mycotoxins is the result of the natural biological process of funghi and has occurred over thousands of years. However, mycotoxin production has been influenced by climate change and changes in agricultural practise.
Mycotoxins are produced by a wide range of funghi including Aspergillus (Aflatoxin and Ochratoxin), Fusarium, (Zearalenone, Deoxynivalenol, Fumonisin) and Penicillium (PR toxin and Roquefortin). These toxins have a considerable pharmacological effect, even at very low concentrations (parts per billion), while toxicity may be further enhanced by metabolism in vivo, particularly by the liver. Detoxification of most toxins occurs in the liver, while in the gastro-intestinal tract (GIT), under certain conditions, detoxification may also be achieved by micro-organisms.
A large number of mycotoxins have been identified. Currently, there are five main groups of particular agricultural interest: the Aflatoxins, the trichothecene (for example Deoxynivalenol), the Zearalenone group, the Fumonisins and the endophyte toxins.
Aflatoxins can cause growth reduction, suppressed immunity, reduced feed efficiency and increased mortality in cattle, among other symptoms. In pigs, reduced feed efficiency, increased mortality, and lower growth rates can be observed. In poultry, there are similar symptoms and a decreased ability to metabolize fat, protein and starch.
Zearalenone in cattle and pigs mimics oestrogen and produces a considerable reduction in reproductive performance, reduced growth, reduced milk production and reduced feed efficiency. In poultry, increased mortality is observed.
Deoxynivalenol (DON), an example of a trichothecene, causes severe symptoms in cattle, pigs and poultry, including gastric effects such as vomiting, reduced growth rates, reduced egg production, scours and reduced feed efficiency.
Fumonisin produces negative effects via a reduction in blood circulation and cardiac output, at least in part by agonising sphingosine receptors. In this way they reduce growth and cause pulmonary oedema in swine and poultry. This reduction of circulation affects all major organs including the liver and can exacerbate and enhance the effects of other toxins that may also be present.
Ochratoxin can be carcinogenic in man and produces immuno-supression in farm animals.
Lolitrem B (Acremonium lolii in Ryegrass) is an example of an endophyte toxin that produces a form of grass staggers often confused with hypomagnesaemia.
Sporidesmin (Pithomyces spp. in Ryegrass) is an endophyte that causes facial eczema and liver damage in sheep.
Ergovaline (Acremonium coenophialum) is an endophyte toxin found in tall fescue, which reduces prolactin release and reduces blood flow.
It is in the interests of the health of both humans and animals that mycotoxins are reduced, or preferably removed altogether, from the food chain.
Current techniques used to reduce mycotoxin content in a foodstuff involve the use of mycotoxin-binding agents, such as bentonite clay, to which the toxins bind and can therefore be removed with the clay. However, binding and removal of mycotoxins are only partly successful. Some mycotoxins remain toxic even when attached to a binding agent, while some toxins do not bind efficiently at normal in vivo concentrations. Higher contamination levels are also an issue as the current recommended levels of binders may not be sufficient to remove all toxins present.
An alternative technique is to add to foodstuffs enzymes, or microorganisms, that break down mycotoxins, to reduce toxicity. However, this is often not effective at reducing mycotoxin content sufficiently, which may be due to a dynamic equilibrium in the gasto-intestinal tract, which prevents excretion of the toxins.
An effective technique for reducing mycotoxin toxicity is therefore still required.